Pulse oximeters perform a spectral analysis of the pulsatile component of arterial blood in order to determine oxygen saturation, the relative concentration of oxygenated hemoglobin to depleted hemoglobin. Pulse oximeters have gained rapid acceptance in a wide variety of medical applications, including surgical wards, intensive care units, general wards and home care by providing early detection of decreases in the arterial oxygen supply, reducing the risk of accidental death and injury. A pulse oximetry system consists of a sensor, a monitor and a patient cable providing electrical communication between the sensor and monitor. The sensor attaches to a patient tissue site and provides a physiological signal to the monitor, which continuously displays patient oxygen saturation and pulse rate measurements.
A pulse oximetry sensor has emitters typically consisting of a red light emitting diode (LED) and an infrared LED that project light through blood vessels and capillaries underneath a tissue site, such as a fingernail bed. The sensor also has a detector typically consisting of a photodiode positioned opposite the LEDs so as to detect the emitted light as it emerges from the tissue site. Sensor types include a disposable sensor and a reusable sensor. A disposable sensor attaches to a patient tissue site with an adhesive wrap and is intended for use by only a single patient. A reusable sensor clips onto a patient tissue site and is intended for repeated use on multiple patients.
FIG. 1 illustrates a reusable finger sensor 100 having a sensor clip 200, a sensor connector 110 and a sensor cable 120. The sensor clip 200 has an open position for inserting a finger, typically the index finger, and a close position (shown) for securing the sensor clip 200 to opposite sides of the finger. The clip 200 has a front end 201 and a back end 202. A finger is inserted into the front end 201 in the open position. The clip 200 is moved between the close position and the open position by pressing on and releasing the finger grips 205 at the back end 202. A spring 280 (FIG. 2) applies force to the back end 202 that determines the pressure on an inserted finger in the closed position. The sensor clip 200 is described in further detail with respect to FIG. 2, below.
Also shown in FIG. 1, the sensor connector 110 plugs into a patient cable (not shown). The sensor cable 120 has a first end 122 terminating at the sensor clip 200 and a second end 124 terminating at the sensor connector 130. The sensor cable 120 electrically communicates monitor originated LED drive signals from the connector 110 to the sensor clip 200 and monitor destined detector signals from the sensor clip 200 to the connector 110.
FIG. 2 further illustrates a reusable sensor clip 200 having a top shell 210, a top pad 220, a bottom pad 230, a bottom shell 240, an emitter 250, a detector 260, hinge pins 270 and a spring 290. The top shell 210 and top pad 220 retain the cable 120 and emitter 250 to form a top jaw 208. The bottom shell 240 and bottom pad 230 retain the detector 260 to form a bottom jaw 209. The clip 200 is assembled with the hinge pins 270 inserted through hinges 214, 244 and the spring 290 so as to rotatably attach the jaws 208, 209 and retain the spring between the jaws 208, 209. The spring 290 has legs 292 that apply force to the top shell 210 and a center section 294 that applies tension to the bottom shell 240, urging the jaws 208, 209 to a closed position in which the pads 220, 230 are held against a tissue site. Pressure sensitive adhesive (PSA) 282, 288 adheres the emitter 250 to the top shell 210 and the detector 260 to the bottom shell 240. Windows 284, 286 pass light from the emitter 250 to the detector 260. A finger is inserted into the clip 200 in an orientation shown on the top shell 210.